Aircraft gun mount



Aug. 7, 1945. H. F. FRANKLIN AIRCRAFT GUN MOVUNT Filed Sept. 4, 1943 2 Sheets-Sheet l V mmvrm hubeff 'E Fran/(11h Aug. 7, 1945. H. F. FRANKLIN AIRCRAFT GUN MOUNT Filed Sept. 4 1945 2 Sheets-Sheet 2 DD F W 2N 1 INVENTOR. BY Huber? fiwn/r/m W mfm tiyely large, among other reasons full-range adjustment of gun elevation for the respective flight-angles at different air-speeds.

one of the objects of e an improved gun mount of the character reappear.

Patented Aug. 7, 1945 AIRCRiiFT-GUN MOUNT Hubert F. Franklin, Baldwin, N. Y., assignpr to Republic Aviation of Delaware Corporation, a corporation Application September 4, 1943, Serial No. 501,224 6 Claims. (01. 89-415) concerned with cases where the wing-type machine gun is mounted on mounts that are preferably adjustable ones, and theconstruction issuch that thegun and its muzzle lie entirely inside the contour of the wing, the gun firing through an opening in the leading ed e thereof. The adjustment is made in such manner that the position of the gun, with reference to the fore-and-aft axis of the plane, gives the desired alignment for With the various constructions of gun mounts proposed heretofore, ing edge or the wing has unavoidably been relato allow for Such a relatively large opening appreciably weakens the wing structure and necessitates substantal reenforcement and a corresponding increase in weight. Due to aerodynamic reasons it also necessitates the employment of shutter-means for closing said opening when not .inuse.

With the foregoing situation in view, it is this invention to provide ferred to which has all the advantages of those of the prior art, but which will entail, in addition, a substantial decrease in the diameter of fire-opening in the leading edge of the wing.

In accordance with the invention, for any and all adjustments, or angles of elevation of the gun, the respective lines of fire substantially meet, or intersect, at a theoretical or in close proximity to, the leading edge of the wing. In short, the virtual pivot made to lie substantially at the muzzle itself. Therefore, the fire-opening in the leading edge of the wing, 'need be only slightly larger'than the bore of the gun.

Another feature resides present improved construction, operational advantages are of but one adjustment.

in the fact that in the all the desired a given flight-path angle.-

of the gun is the opening in the leadobtained by means Otherobjects and advantages will hereinafter For th purpose of illustrating the invention,

' an embodiment thereof is shown in the drawings, wherein fragmentary, elevational Fig. l is a simplified,

operating action or the view, illustrative of the Fig. 2 is a simplified, side elevational view of one embodiment of my invention;

Fig. 3 is a side elevational view, tion,'of another embodiment of my' invention, the section being taken on the line 3-3 in Fig. 4; Fig. 4 is a plan view of Fig. 3, some of the parts being removed for the sake of cleamess; and

Fig. 5 is an 5-5 in Fig. '3.

In order to more clearly set forth the concepts and nature of the present invention, it is desirable to compare same with the most relevant of the prior art. In said prior art construction, shown in Fig. l, the front mount Ill supports the gun II for elevational adjustment about a fixed pivot l2. The two extreme .positions of adjustment are represented by the longitudinal center lines It and 15. The adjacent portion iii, of the leading edge of the wing within which the gun-1s mounted, is shown proscrew-and-nut 'or other suitable construction,

whereby the gun can be elevated or depressed about the pivot or pivotal supporting point'li, and fixed or locked in the desired position of adjustment. An example of such an arrangement is shown in Patent No..1,939,699,' issued Dec. 19, 1933, to Clarence F. Hofstetter.

In contrast, in the embodiment of the present invention which is shown in Fig.. 2, the front and rear mounts of the gun Ila are designated generally by the reference numerals lilo and Nb, respectively. extreme positions of adjustment in Fig. 2 are represented by the center lines a and lid, re-

spectively.

Connection between the gun andythe front mount Illa may be made by means or two belicranks 16, disposed, respectively, on sides of the gun and pivotally connected thereto to provide the pivot. or pivotal point of support 12a, corresponding to the pivot l2 in Fig.

15 are pivotally connected 1. The bell-cranks at H to the respective sides. 88 or the U-shaped base for the front mount. which base is fixed to some suitable part of the wing structure, as reppartly in secenlarged sectiontaken 'on'the line of adjustment, one of which Corresponding to Fig. 1, the two opposite resented in the drawing. For the purpose of imparting pivotal and simultaneous movement to the members I 5 about the pivot II, a wormgear segment I9, which meshes with a worm fixed on a shaft 2|, is common with respect to,

and joins the members l6.

Similarly, connection between the gun and the rear mount IIlb, may be made by means of two bell-cranks 22 disposed, respectively, on opposite sides of the gun. These bell-cranks are joined by a pin-and-slot connection comprising a bolt or pin 23 which has a sliding fit in a slot 24. The slot 24 is made in a lug 25 which may be integral with the gun casing. The bell-cranks 22 are pivotally connected at 26 to the respective sides 21 of the U-shaped base for the rear mount, which base is suitably secured to the wing structure. A worm-gear segment 28, which meshes with a worm 29 fixed on shaft 2I, is common with respect to, and joins the members 22. The shaft 2|, which may be journalled in the respective bases of the front and rear mounts, is rotated by turning a wheel 30 fixed on one .end of the shaft.

The pitch of worm 20 is opposite to that of the worm 29, so that when the wheel 30 is turned in the direction to depress the muzzle of the gun, the bell-cranks I6 rotate counter-clockwise about pivot I1, and ,the bell-cranks 22 rotate clockwise about pivot 26. Turning the wheel in the other direction to elevate the muzzle of the gun, causes bell-cranks I6 to rotate clockwise about pivot I1, and bell-crank 22 to rotate counter-clockwise about pivot 26.

In the full-line position of the gun, the longitudinal axis of the gun is as shown at 9a. In the extreme position for maximum gun-muzzle depression, the bell-cranks I5 and 22 are in the broken-line positions shown, respectively, at 16a and 22a, and the longitudinal axis of the gun muzzle is as shown at Ma. In the extreme position for maximum gun-muzzle elevation, the bellcranks I6 and 22 are in the broken-line positions shown, respectively, at I61: and 22b, and the longitudinal axis of the gun muzzle is as shown at I5a.

The respective dimensions of the various parts are such that in all positions of elevational ad- .iustment of the butt or rear portion IIa of the gun, the longitudinal axis of the gun muzzle, or in other words, the line of fire, passes substantially through one and the same point 3|. This theoreticalfocal point 3| always lies closely adjacent to the muzzle, in the direction of fire, and always lies either in, or in close proximity to, the fire-port I'm in the leading edge I6 of the wing. On account of this construction and manher of operation, with the muzzle of the gun kept back within the wing and mounted for elevational adjustment through a desired range, the

opening may be retained relatively small as com- I pared to the openings necessary heretofore. In addition, the previous necessity for providing a blast tube to protect the skin and parts from incandescent gases is entirely obviated.

In that embodiment ofthe invention which is shown in Figs. 3, 4'and 5, the various parts have been designated by the same reference numerals as the corresponding and respective parts in Fig.

' 2, but with the sufilx c, and in this embodiment,

the two bell-cranks I60, which form part of the front mount, are pivotally connected to the gun IIc to provide the pivot orpivotal point of support I20. The bell-cranks I 60 are, in turn, pivotally connected at Ilc to the respective sides lie 9,881,841 of a U shaped bracket for the front mount, which bracket is fixed to the front spar of the wing, as shown.

The two bell-cranks 22c are joined by a bolt or pin 23c which has a sliding fit in a slot 24c with which the gun-mount bracket 32 is provided. The members-22c are pivotally connected at 26c to the respective sides 210 of the U-shaped base 82 for the rear mount, which base is secured to the ribs of the wing.

A power shaft 2Ic is journalled in base 33, and is connected to an electric motor 34 and, through a universal joint I00, to a screw 2Id. The collars or shoulders shown provide thrust bearings to prevent. axial movement of shaft 2Ic with respect to base 33. The screw 2 Id is provided with a right-hand thread, and carries a nut 35. The other part, 2le, of this screw is provided with a left-hand thread, and is screwed into the adjacent end of a shaft I90. The other end of shaft I is pivotally connected to the bell-cranks I60, as shown. The nut 35 is provided with diametrically opposed trunnions 38 which have a sliding fit in grooves 31 in the respective faces of hellcranks 22c, as best seen in Fig. 5.

In Fig. 3, the gun is shown in the position of maximum muzzle-depression, the longitudinal axes 9c and Me of the gun muzzle corresponding, respectively, to the axes 9a and Ma in Fig. 2. When the motor 34 is operated in the direction to cause elevation of the gun muzzle, the nut 35 travels to the right, in Fig. 3, on the threaded part 2Id of shaft 2Ic. This action causes counter-clockwise movement of members 220 about the fixed axis 26c. concomitantly with the rotation of threaded portion 2Id, the left-handpitched, threaded part 2Ie of shaft 2Ic is also being rotated, and imparts movement of the shaft to the left, and thence imparts clockwise rlnovement of members IGc about the fixed axis As in Fig. 2, the respective dimensions or the various parts in Fig. 3 are chosen such that in all positions of adjustment of the gun He, the line of fire passes substantially through a focal point immediately beyond thegun structure per se, in the direction of fire. This focal point is either at or in close proximity stricted fire-opening designated generally at 3|.

. In the present improved gun-mount, the handwheel 30 in Fig. 2 and the motor 34 in Fig. 3, constitute, in each case, single operating means for making all elevational adjustments. Operation of the handwheel or motor in one direction causes gun-butt-depressing action of both the frontand rear mounts simultaneously, whereas operation in the opposite direction causes gun butt-raising action of both mounts simultaneously. However, for any incremental adjustment, either to increase the lowering of the gunmuzzle or to increase the raising thereof, and

throughout the. entire operational range, the

gun-butt-raising and gun-butt-depressing actions of the front mount are always effected in to the very materially reand outside all the gun structure per se, in the direction of fire.

It will be understood that various changes, such as the size, shape and arrangement of the parts, may be made without departing from the spirit of this invention or the scope of the claims.

The inventive concepts and several illustrative embodiments thereof having been thus disclosed in the manner required by the statutes, what is claimed as new, is:

1. In a gun mount having spaced front and rear trunnions adjustable in elevation: a common control shaft to adjust simultaneously and differentially the elevation of said front and rear trunnions, two independent bell-cranks fulcrumed to a fixed structure, each of said bellcranks having an upper arm pivoted to a gun trunnion and a lower arm connected to said common control shaft.

2. In a gun mount having spaced front and rear trunnions adjustable in elevation: a common control shaft to adjust simultaneously and differentially the elevation of said front and rear trunnions, two independent bell-cranks fulcrumed to a fixed structure, each of said bellcranks having an upper arm pivoted to a gun trunnion and a lower arm connected to said common control shaft, and each of said upper arms being substantially parallel to the axis of the gun in order to act as a strut to transmit directly to said fixed structure the recoil and counterrecoil loads.

3. In a gun mount having spaced front and rear trunnions adjustable in elevation: a common control shaft to adjust simultaneously and differentially the elevation of said front and rear trunnions, two independent bell-cranks fulcrumed to a fixed structure, each of said bellcranks having an upper arm pivoted to a gun trunnion and a lower arm connected to said common control shaft, at least the upper arm of the front bell-crank being substantially parallel to the axis of the gun in order to act as a strut to transmit to said fixed structure directly and substantially without vertical component the axial loads acting on the gun.

4. The combination with an aircraft winghaving spaced front and rear internal supporting structures and a gun having spaced front and rear trunnions, said wing having a circular fireport in its leading edge in alignment with the gun and of a diameter equal substantially to the muzzle diameter of the gun: of an adjustable gun mount comprising crumed to said front supporting structure and having one of its arms pivoted to the front trunnion of the gun, a rear bell-crank fulcrumed to said rear supporting structure and having one of its arms pivoted to the rear trunnion of the gun, and common differential operating means connected to the remaining arm of each of said bellcranks to swingsaid bell-cranks simultaneously and differentially in opposite directions about their respective fulcrums to adjust the gun about a front bell-crank fulbell-cranks fulcrumed to said tween the a common control screw mounted for rotation in a virtual pivot located at or near the center of said fire-port.

5. The combination with an aircraft wing having spaced front and rear U-brackets and a gun having front and rear trunnions mounted on said brackets, said wing having a circular fire-port in its leading edge in alignment with the gun and of a diameter substantially equal to the muzzle diameter of the gun: of a vertically adjustable gun mount comprising a pair of parallel front bell-cranks fulcrumed to said front U-bracket and having their upper arms pivoted to the front trunnion of the gun and their lower arms joined together, a pair of parallel rear bell-cranks fulcrumed to said rear U-bracket and having their upper arms secured by pin-and-slot connections to the rear trunnion of the gun and'their lower arms joined together, toothed helicoidal sectors formed on said joined ends of the front and rear sets of the bell-cranks, a common control shaft mounted for rotation in said U-brackets, and a pair of worms mounted on said shaft one to mesh with each of said sectors, the pitches of said worms and segments being different and opposed whereby the rotation of the shaft in either direction swings said bell-cranks simultaneously and differentially in opposite directions about their respective fulcrums to adjust the angle of elevation of the gun about avirtual pivot located at or near the center of said fire-port.

6. The combination with an aircraft wing having spaced front and rear spars and a circular fire-port in its leading edge andv a gun having front and rear trunnions aligned with said port: of a vertically adjustable gun mount comprising spaced front and rear U-brackets fixedly secured to the corresponding spars, a pair of parallel front bell-cranks fulcrumed to said front U- bracket and having their upper arms pivoted to said front trunnion, a pair of parallel rear rear U-bracket and having their upper arms secured by a pin-andslot connection to said rear trunnion, an internally threaded non-rotatable hollow shaft pivotally connected with the lower arms of said front bell-cranks, a nut secured against rotation belower arms of said rear bell-cranks,

said threaded hollow shaft, in said nut and in said rear U-bracket, and means mounted on the rear U-bracket. to revent longitudinal movement of said screw, the thread of that part of the screw cooperating with the shaft being opposed to, and of different pitch than, the thread of the part of the screw whereby the rotation of this screw in either direction swings said front and rear bell-cranks simultaneously and differentially in opposite directions about their respective fulcrums to adjust the angle of elevation of the gun by rotating said latter about a, virtual pivot located at or near the center of said fire-port.

HUBERT F. FRANKLIN.

cooperating with the nut, 

